<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>vue计数器</title>
    <script src="https://cdn.staticfile.org/vue/2.6.11/vue.js"></script>
  </head>
  <body>
    <div id="app">
      <div id="input-num">
        <button @click="sub">-</button>
        <span>{{num}}</span>
        <button @click="add">+</button>
      </div>
    </div>
    <script>
      var app = new Vue({
        el: "#app",
        data: {
          num: 1
        },
        methods: {
          add: function() {
            if (this.num < 10) {
              this.num++;
            }
          },
          sub: function() {
            if (this.num > 0) {
              this.num--;
            }
          }
        }
      });
    </script>
  </body>
</html>
